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英国驻华使馆气候变化参赞康大卫

 
 
 

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气候变化博客——开启!  

2009-11-16 17:00:47|  分类: 默认分类 |  标签: |举报 |字号 订阅

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作为一个深入研究气候变化的外交官所面临的众多挑战之一就是要跟得上最新的科学进展。

对当前或者是未来全球气候变暖影响的新证据正不断地被发布。但是,联合国政府间气候变化专门委员会的正式评估大约每6年才重新做一次。最新一次评估是在2007年做的,而且只涵盖了截止到2006年5月出版的同行评估期刊中所发表的科学研究。

自那时到现在,无论是在地球上的气候体系,还是证据基础方面都出现了许多新情况。到哪里去获得基于最新研究形成的观点呢?

我要推荐国际研究型大学联盟(International Alliance of Research Universities)基于今年早些时候的哥本哈根会议撰写的一份“综合”报告。全文以英文著述的报告于6月份发表,但是现在已经有了其他语言版本,包括中文版。世界上最优秀的一些气候专家参与了该报告的撰写。报告的明确目标就是要反映自从上次政府间气候变化专门委员会的报告以来所做的“坚实而准确”的研究。重要的是,报告经历了一个广泛的评估过程。

报告讲述了气候变化的物理效应发展的速度如何比之前预想更快。海洋温度上升比2007年政府间气候变化专门委员会的报告所说的温度高50%。对未来全球海平面上升的预计是政府间气候变化专门委员会预测的两倍。冰冠和冰层正以更加快的速度大量消失,在夏天缩减的程度更大。有更多更确凿的证据表明气候变化对自然过程所造成的威胁,而自然过程能够让土地和海洋担当碳“汇”的重任。

报告分析了这些对定义气候变化的“危险性”意味着什么。许多国家的政府(包括英国)已经形成确立的观点,那就是我们需要一个强有力的国际气候协议,而这个协议要足够将全球变暖限制在比工业革命之前高出不超过2度的范围内。这一底线之上的如何情况都有可能带来更大的风险。

但是,不是所有国家都明确表示支持升温幅度控制在2度范围内的目标,或者是承诺采取措施达到这一目标。那么最新的证据对于升高2度,或者3度、4度所带来的风险说明了什么?

2001年,政府间气候变化专门委员会评估了五类与气候变化相关的焦点问题(如极端天气事件的风险,或大规模自然系统突变的风险)。在那时,研究表明把温度升高限制在2度以内足以避免所有五类中严重的风险。令人遗憾的是,情况已经发生了改变。在新的“综合”报告中最新的分析认为升温2度带来的风险水平大幅度提高了。举例来说,大规模自然系统突变和发生不可逆转改变的风险程度对升高2度的旧评估 从“非常低”提高到新报告中的“中等”。换句话说,新报告中温度升高2度的风险值与旧报告中升高最少3度的风险值相等。

报告总结说:“虽然温度比工业革命之前升高2度仍然被人们最普遍地说成是能够避免危险气候变化的最低阀值,但是却要承担为社会和环境带来有害性影响的巨大风险。”

关于我们应该在何处划上气候变化的分界线这个问题,当然是国际谈判的根本问题,而国际谈判将在12月份的哥本哈根会议上达到顶点。一些政策制定者和政府无疑将继续建议维持2度的目标过高,而且没有科学依据。我从最新的研究中获得的信息恰恰相反。2度的目标也许还不够高。


Blog Action Day: The physical impacts of climate change

One of the many challenges of being a diplomat specialising in climate change is keeping up with the latest science.

New evidence on the present and likely future impacts of global warming is being published all the time. But formal assessments by the UN’s Intergovernmental Panel on Climate Change appear only once every six years or so. The last one was in 2007 and only covered science published in peer review journals up to May 2006.

A lot has happened since then, both to the planet’s climate systems and the evidence base. Where to go for an informed view of the latest science?

I can recommend a “synthesis” report based on a conference held earlier this year in Copenhagen by the International Alliance of Research Universities. The report was published in English in June but is now available in other languages too, including Chinese . Some of the world’s best climate experts were involved in writing it. Its stated goal is to reflect “solidly and accurately” the research produced since the last IPCC report. Importantly, it was subject to an extensive review process.

The report describes how the physical impacts of climate change are kicking in faster than previously thought. Ocean warming is now 50% greater than reported in the 2007 IPCC report. Estimates of future global sea level rise are double the IPCC projections. Ice caps and ice sheets are losing mass faster, and shrinking more in the summer. There is now more – and better – evidence on the threat posed by climate change to natural processes that enable land and oceans to act as crucial “sinks” for carbon.

The report analyses what all this means for the defining of  “dangerous” in the context of climate change. Many governments (including the UK’s) have a settled view that we need an international climate agreement strong enough to limit global warming to no more than 2 degrees above pre-industrial levels. Anything less we argue would be too risky.

But not all governments are explicitly supporting the 2-degree target or yet pledging actions in line with achieving it. So what does the latest evidence say about the risks of 2 versus, say, 3 or 4 degrees of warming?

In 2001 the IPCC assessed five categories of concern linked to climate change (eg the risk of extreme weather events or the risk of abrupt changes in large natural systems). Back then, the science indicated that limiting warming to no more than 2 degrees would be enough to avoid serious risks across all five categories. Sadly that is no longer the case. An updated version of the analysis in the new “synthesis” report assigns significantly higher levels of risk to 2 degrees of warming. For example, the risk of abrupt and irreversible changes in large natural systems increases from “very low” in the old assessment of 2 degrees to “moderate” in the new one. In other words, 2 degrees worth of risk in the new analysis resembles at least 3 degrees worth of risk in the old one.

The report concludes: “Although a 2 degree rise in temperature above pre-industrial remains the most commonly quoted guardrail for avoiding dangerous climate change, it nevertheless carries significant risks of deleterious impacts for society and the environment”. 

The issue of where we should agree to draw the line on climate change is of course fundamental to the international negotiations that will come to a head in Copenhagen in December. Some policy makers and governments will no doubt continue to suggest that aiming for 2 degrees is too ambitious and not justified by the science. The message I take from the latest research is just the opposite. Aiming for 2 degrees may not be ambitious enough.

 

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